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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In patients with severe respiratory disease, the work of breathing is increased and the respiratory muscles, particularly those of inspiration, may become fatigued. Hitherto, there has been little information on the incidence of respiratory muscle fatigue in acutely breathless patients. We studied 34 patients with severe respiratory disease on admission to hospital when they were most breathless, and then, if possible, 7 to 14 days later after recovery for evidence of sternomastoid muscle fatigue or increased fatigability. Frequency/force curves, numerically expressed as the 20:50 ratio, were carried out in all patients on admission. Three of the 34 patients had evidence of low frequency fatigue (i.e., greater than 15% reduction in 20:50 ratio) in the sternomastoid muscle on admission when first studied (mean +/- SEM 20:50 ratio, 56.3 +/- 1.2%; n = 3). The mean 20:50 ratio in the remaining 31 patients on admission was 75.7 +/- 1.6% (n = 31) compared with 77.8 +/- 1.4% (n = 25) when symptomatically better (p less than 0.05). The mean 20:50 ratio on admission was also significantly lower than the mean 20:50 ratio in a group of age- and sex-matched normal control subjects (i.e., 78.5 +/- 1.4%, n = 25; p less than 0.05). Twenty-five patients were studied completely both on admission and recovery, including a fatigability test that involved the performance of 50 fatiguing head lifts with measurements of the 20:50 ratio 10 and 60 min later. Sternomastoid muscle fatigability was significantly increased on admission when the patients were most breathless, compared with recovery when they were less breathless (p less than 0.001 at both 10 and 60 min).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sternomastoid muscle function and fatigue in breathless patients with severe respiratory disease. 367 71

Pulmonary functions at rest and cardiorespiratory responses to low speed treadmill walking were investigated in 24 patients (P), (mean age, 38 years; range, 20 to 56 yr) with multiple sclerosis and compared with a control group (C). The following parameters were significantly (p less than 0.01) different in P from those in C. At rest in P, the residual volume to TLC ratio was 21% greater, respiratory muscle strength index was 28% lower, and heart rate (HR) was 11 beats/min-1 higher. During treadmill walking at a given speed, HR, minute ventilation (VE), and O2 consumption (VO2) were all elevated (37 to 119%). In addition, the energy cost of walking, per unit distance, above resting, was 2 to 3 times greater, with mean +/- SEM values for P of 0.299 +/- 0.019 and C of 0.147 +/- 0.006 at 2 km/h and 0.275 +/- 0.042 and 0.110 +/- 0.005 (for P and C, respectively) ml O2 kg-1 m-1 at 4 km/h; the HR and VE/VO2, also when referred to a given VO2, were higher. We conclude that a high energy cost of walking may be an important contributing factor to breathlessness and leg fatigue in patients with multiple sclerosis. Poor conditioning, altered cardiovascular control, and respiratory muscle weakness may play additional roles.
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PMID:Energy cost of walking and exertional dyspnea in multiple sclerosis. 377 62

It is not certain to what extent low frequency fatigue affects the performance of a muscle. We studied the endurance capacity of the sternomastoid muscle to undergo repetitive isometric neck flexion contractions for 2 s every 4 s at 35% of its maximal voluntary contraction force (MVC) in 5 normal subjects starting with different levels of fatigue. The endurance time, the duration the subjects were able to achieve the target force before exhaustion, was measured in each subject on 3 occasions: Study 1: in the fresh state, with a normal frequency/force curve and 20:50 ratio (ratio of force response at 20 Hz to that at 50 Hz) before the start of the endurance exercise; Study 2: with a moderately reduced 20:50 ratio before the start of endurance exercise (mean +/- SEM reduction in 20:50 ratio 11.4 +/- 0.8%); Study 3: with a substantially reduced 20:50 ratio before the start of the endurance exercise (29.2 +/- 3.7%). These reductions in 20:50 ratio were produced by the subjects performing 150 isometric neck flexion contractions at 50% of their MVC, followed by a period of rest to allow the 20:50 ratio to recover to approximately 10% of the starting value in Study 2, and to within 20 to 40% of the starting value in Study 3. Endurance exercise was then carried out.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effect of low frequency fatigue on endurance exercise in the sternomastoid muscle of normal humans. 396 31

The direct smooth muscle vasodilator hydralazine has been used to treat exertional fatigue in patients with chronic heart failure. However, prior studies suggest that arteriolar vasodilators such as hydralazine may actually impair nutritive flow to working skeletal muscle by interfering with the distribution of blood flow within muscle. To investigate this possibility, tension development and metabolism were measured in nine vascularly isolated gracilis muscle preparations perfused at 90 mm Hg and stimulated to contract progressively at rates of 1, 3 and 6/s with each stage lasting 3 minutes. Studies were then repeated after 30 minutes of intraarterial hydralazine (0.02 to 0.12 mg/min). At rest, hydralazine decreased mean vascular resistance (+/- SEM) from 15.1 +/- 1.4 to 8.6 +/- 0.9 X 10(2) units (p less than 0.001) and increased blood flow from 6.4 +/- 0.7 to 11.4 +/- 1.2 ml/min (p less than 0.001), but did not change oxygen consumption (VO2) control, 18 +/- 1 versus hydralazine, 17 +/- 2 microliter/min). Hydralazine also decreased vascular resistance and increased flow at a contraction rate of 1/s, but not at 3 and 6/s. Hydralazine had no effect on maximal VO2 (control, 254 +/- 18 versus hydralazine, 236 +/- 19 microliter/min), maximal developed tension (control, 353 +/- 90 versus hydralazine, 334 +/- 74 kg X min) or the response in venous lactate (control, 20.6 +/- 2.3 versus hydralazine, 18.1 +/- 2.0 mg/dl). Hydralazine also did not change muscle metabolism and function at contraction rates of 1 and 3/s. These data suggest that hydralazine does not adversely affect nutritive flow to working skeletal muscle.
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PMID:Effect of hydralazine on nutritive flow to working canine gracilis skeletal muscle. 647 Mar 32

Complement (C) activation, neutropenia, and mild pulmonary dysfunction attend hemodialysis (HD) with cellophane [for example, cuprophan (Cu)] membranes. While usually asymptomatic, these phenomena may cause distress in patients with cardiopulmonary disease, and "start-up" symptoms of HD might be mediated by C-stimulated granulocytes (PMNs). Cellulose acetate (CA) hemodialysis membranes have been devised and claimed more blood compatible than Cu. In a blinded series of HD patients, pruritus, fatigue, and sense of well-being were each scored statistically more favorably by the patients during HD with CA than during HD with Cu (P less than 0.05). Postulating that less C activation might underlie the benefit, we showed that neutropenia was less severe with CA (nadir 77.6% of initial count, +/- 4 SEM) than with Cu (38.3% +/- 2.9; P less than 0.01). In vitro, incubation of CA membranes with plasma led to less C3 conversion (20% vs. 40%), less PMN aggregating activity (5.9 ZAP units vs. 36.3) and less decrement in CH50 (6.5% vs. 22%) than like incubations of Cu. C activation was also less potent in vivo: During HD plasma C3a rose from a mean 401 ng/ml to a peak 6,325 in patients on Cu dialyzers, but from 426 to only 3,637 in patients on CA devices (P less than 0.05). Time-course studies suggested CA was initially as potent an activator as Cu but rapidly lost ability to activate C, possibly because of saturation of C3b binding sites. As an index of PMN activation, we also assayed plasma lactoferrin and found levels significantly higher during Cu than CA dialysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Symptoms and activation of granulocytes and complement with two dialysis membranes. 660 68

Skeletal muscle function, body composition (total body nitrogen and total body potassium) and standard parameters of nutritional assessment were measured in six severely depleted patients with primary anorexia nervosa, both on admission and during oral refeeding. The function of the adductor pollicis muscle was assessed by electrical stimulation of the ulnar nerve. On admission muscle function was markedly abnormal in the patients with anorexia nervosa (n = 6) compared with normal subjects (n = 22), with a significant increase in the force of contraction at 10 Hz, with a mean +/- SEM of 48.0 +/- 3.7% and 28.8 +/- 1.2%, respectively (p less than 0.001). There was slowing of the maximal relaxation rate, 6.6 +/- 0.6% and 9.6 +/- 0.2%, respectively (p less than 0.001) and increased muscle fatigue 18.6 +/- 5.9% and 3.5 +/- 0.8%, respectively (p less than 0.01). Initially, the mean serum albumin was normal (4.0 +/- 0.1 g/dl), although there was evidence of severe depletion of somatic protein stores, with a low total body nitrogen and creatinine-height index. Within 4 wk of oral refeeding, maximal relaxation rate and muscle fatigability were restored to normal, and within 8 wk all parameters of muscle function were normal. During the study total body nitrogen increased by only 13% and was still 19.4% below the predicted normal total body nitrogen, whereas total body potassium increased by 32% and body fat by 46%. Normalization of muscle function may be related to restoration of muscle electrolytes rather than repletion of body nitrogen.
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PMID:A comparison between muscle function and body composition in anorexia nervosa: the effect of refeeding. 688 Oct 81

Grit blasting is a common procedure of roughening surfaces to promote physical attachment of porous coatings, but it has been shown to reduce fatigue strength. Shot peening is known to increase fatigue strength by inducing compressive surface stresses; however, it is not known how subsequent grit blasting affects these benefits. This study examines the endurance limits, Se, of ELI grade Ti-6A1-4V specimens under rotating cyclic bending, including polished (control); belted and beaded; belted, beaded, and grit blasted; and belted, beaded, shot peened, and grit blasted. Belting and beading resulted in a slight increase in Se, grit blasting caused a 15% reduction in Se from polished. Fifty percent of this reduction was recovered when shot peening preceded grit blasting, suggesting that residual compressive surface stresses, induced by peening, were not eliminated by the blast process. Roughness averages and RMS values did not correlate with Se trends. SEM results showed classical fatigue fractures, consistent with surface crack initiation.
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PMID:Effects of precoating surface treatments on fatigue of Ti-6A1-4V. 749 7

Can L-sugars contribute to whole body energy metabolism? Energy balance studies were undertaken in rats fed L-sugars at a rate of 10 g/100 g basal diet. Partial metabolizable energy values (MEVp) during the last 28 of 56 d while consuming the L-sugar diets showed that L-glucose contributed no energy (0.3 +/- 0.9 kJ/g, P > 0.5, mean +/- SEM), whereas L-fructose and L-glucose contributed 6.9 +/- 0.9 (P < 0.001) and 8.8 +/- 1.8 (P < 0.001) kJ/g, respectively. Over periods from 0 to 28 and 0 to 56 d of L-sugar treatment, measurements were made of energy intake, the average lean mass of animals, fat and lean mass deposition. Using these measurements and a computational model, estimates were made of each supplement's net metabolizable energy value for maintenance (NEVs). These estimates confirmed the supply of energy from L-fructose, with NEVs of 5.6 +/- 3.2 (P < 0.32) and 6.1 +/- 1.7 (P < 0.01) kJ/g over 28 and 56 d, respectively, and L-gulose with NEVs of 10.2 +/- 3.4 (P < 0.01) and 11.4 +/- 1.8 (P < 0.001) kJ/g over 28 and 56 d, respectively. A lack of energy supply from L-glucose was confirmed with NEVs of -2.6 +/- 3.2 (P > 0.5) and 0.0 +/- 1.6 (P > 0.5) kJ/g over 28 and 56 d, respectively. As reference substrates, sucrose and cellulose gave expected energy values in all determinations. Methods comparison analysis showed no differences between MEVp and NEVS. The assimilation of energy from L-fructose and L-gulose is probably via large bowl microorganisms. These observations show that L-gulose and L-fructose contribute to whole body energy metabolism while L-glucose does not.
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PMID:Whole body metabolism is not restricted to D-sugars because energy metabolism of L-sugars fits a computational model in rats. 750 Jan 80

After a single-blind, 4-week placebo run-in period, 161 patients were randomized to trandolapril 2 mg once daily (n = 54), nifedipine slow-release (SR) 20 mg twice daily (n = 55), or a combination of both drugs (n = 52) for 16 weeks. Morning predosing supine diastolic blood pressure (DBP) was the primary efficacy measurement. After 16 weeks the intention-to-treat analysis showed no significant difference in supine DBP (mean +/- SEM) between trandolapril (-12.4 +/- 1.5 mm Hg) and nifedipine SR (-15.3 +/- 1.4 mm Hg; p = 0.1). However, the combination therapy was more effective (-18.9 +/- 1.3 mm Hg). Normalized blood pressure at 16 weeks was seen with 54% on trandolapril, 63% on nifedipine SR, and 77% on the combination. Adverse events, possibly related to drug, were more common with nifedipine SR (34%) than with trandolapril (17%; p < 0.05), and in comparison with the combination (21%). Drug-related treatment emergent events, reported by more than 3% of patients (fatigue, palpitations, edema, migraine), were seen only in the nifedipine SR and combination groups. Trandolapril 2 mg proved a well-tolerated and effective antihypertensive agent, comparable to nifedipine SR 40 mg. Furthermore, the combination of the two drugs was shown to enhance the antihypertensive effect of the two compounds alone. Adverse events were less common with trandolapril and the combination than with nifedipine SR alone.
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PMID:Comparison of the efficacy and safety of trandolapril and nifedipine SR in mild-to-moderate hypertension. Investigator Study Group. 752 8

The contractile properties of the quadriceps muscle were measured in seven healthy male subjects before, during and after prolonged cycling to exhaustion. Special efforts were made to obtain measurements immediately after exercise. The exercise intensity corresponded to about 75% of estimated maximal O2 uptake and time to exhaustion was mean 85 (SEM 9) min. At the end of the cycling heart rate and perceived exertion for the legs were 94% and 97% of maximal values, respectively. Maximal voluntary isometric force (MVC) had decreased after 5 min of exercise to a mean 91 (SEM 4)% of the pre-exercise value (P < 0.05) and decreased further to a mean 82 (SEM 6) and mean 66 (SEM 5)% after 40-min cycling and at exhaustion, respectively. A new finding was that during recovery reversal of MVC occurred in different phases where the half recovery time of the initial rapid phase was about 2 min. The MVC was a mean 80 (SEM 2)% of the pre-exercise value after 30 min and was not affected by superimposed electrical stimulation. Maximal voluntary concentric and eccentric forces decreased to 74% and 80% of initial values at exhaustion (P < 0.05). The kinetics of isometric contraction expressed as the time between 5% and 50% of tension (rise time) and the time between 95% and 50% of tension (relaxation time) were not significantly affected by the prolonged cycling. The electromechanical delay measured as the time between the first electrical stimulus and 5% of tension decreased from a mean 32 (SEM 1) ms at rest to a mean 26.6 (SEM 0.6) ms at fatigue (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of prolonged exercise on the contractile properties of human quadriceps muscle. 758 87


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